I have estimated Nitric Oxide from tissue homogenate by using griess reagent. From the standard curve, I got a concentration about 12 µM. I have used 100 µl of tissue homogenate. The protein concentration of my homogenate is 5 µg/ µl. I am a bit confused with the expression unit of Nitric Oxide. Should I express the concentration in terms of protein? What is the best way to express Nitric Oxide concentration in tissue? Thanks in advance.